1. Field of the Invention
The present invention relates to a recording medium erasing device that is used, for example, for erasing a video signal or an audio signal on a video floppy disk recorded by an electronic still video camera.
2. Description of the Related Art
In an erasing mode of a conventional erasing device, a rotation speed of a disk is lowered from a standard speed (such as, for example, 3600 rpm) to approximately 1/3 of the standard speed (i.e., 1200 rpm). Then, while the disk is rotated at 1/3 of the standard speed, an erasing signal, having a frequency "f", is recorded on a video track or an audio track of the disk.
Since the rotation speed of the disk is set to 1/3 of the standard speed, if the frequency of the erasing signal recorded on the disk is converted to a frequency at the standard speed, the frequency of the erasing signal is "3f". Namely, although the frequency of the erasing signal on the erasing mode is "f", if the disk is rotated at the standard speed to reproduce the signal on the disk, the frequency of the erasing signal becomes "3f".
Therefore, if the frequency "f" is set to an appropriate value, the frequency "3f" can be set outside the FM frequency band, whereby an audio signal or a video signal recorded on the audio track or the video track is erased.
As described above, in a conventional device, since the erasing signal having a predetermined constant frequency "f" is recorded on the disk rotating at 1/3 of the standard speed, to thereby erase a recorded signal on the disk, the frequency "f" must be high enough to erase the signal. If the value of the frequency "f" is not high enough, the erasing signal is reproduced in a reproduction mode. As a result, when it is determined whether or not an RF (Radio Frequency) signal exists in a reproduced track of the disk, to determine whether the checked track is a recorded track or a non-recorded track, a non-recorded track can be mistaken for a recorded track.
Further, in a conventional device, since the erasing signal having the predetermined constant frequency "f" is generated by a generator, not only must the generator and a switch be provided, but signal lines are needed to transmit a switching signal for controlling the switch, and therefore, the conventional device has a complicated construction.